1. Field of the Invention
The present invention relates generally to an improvement in a plastic structural member such as an automotive vehicle body finisher, and more particularly to a joining structure between plastic parts constituting the plastic structural member.
2. Description of the Prior Art
Recently automotive vehicles have been increasingly provided with a so-called finisher, for example, installed in the rear end of the automotive vehicle body and located between a pair of stoplight assemblies. The finisher is frequently formed by using transparent or semitransparent plastic material such as acrylic resin or polycarbonate in order to provide impression of higher grade to the finisher. Additionally, the finisher is usually constructed, for example, of two plate-like parts joined together to form a one-piece plate type finisher and produced by a so-called simultaneous moulding in which a previously moulded one of the two parts is set in a mould forming a space corresponding to the other part, and then molten plastic material is poured into the space thereby to mould the other part in contact with the previously moulded part. In the thus moulded finisher, the two plate-like parts are in secure contact with each other at a generally flat parting plane.
However the following difficulties have been encountered in such a finisher: The flat parting plane between the two plate-like parts provides a less joining area and accordingly a less joining strength between the two plate-like parts, which may bring the finisher to its breakdown upon acting of force by person's hands. In case where one of the plate-like parts is formed of transparent or semitransparent plastic material, the parting plane can be seen through the transparent or semitransparent one, thus deteriorating appearance of the finisher. Additionally, a gas accumulation tends to be made in the poured plastic material during the simultaneous moulding. This gas accumulation looks whitish after the molten plastic material is solidified, thereby degrading appearance of the finisher.